US20230166379A1 - Technique for controlling motor in handheld electric work machine - Google Patents

Technique for controlling motor in handheld electric work machine Download PDF

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Publication number
US20230166379A1
US20230166379A1 US17/990,884 US202217990884A US2023166379A1 US 20230166379 A1 US20230166379 A1 US 20230166379A1 US 202217990884 A US202217990884 A US 202217990884A US 2023166379 A1 US2023166379 A1 US 2023166379A1
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United States
Prior art keywords
magnitude
motor
work machine
control circuit
loads
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Pending
Application number
US17/990,884
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English (en)
Inventor
Hitoshi Suzuki
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Makita Corp
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Makita Corp
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Assigned to MAKITA CORPORATION reassignment MAKITA CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SUZUKI, HITOSHI
Publication of US20230166379A1 publication Critical patent/US20230166379A1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B23/00Portable grinding machines, e.g. hand-guided; Accessories therefor
    • B24B23/02Portable grinding machines, e.g. hand-guided; Accessories therefor with rotating grinding tools; Accessories therefor
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B23/00Portable grinding machines, e.g. hand-guided; Accessories therefor
    • B24B23/02Portable grinding machines, e.g. hand-guided; Accessories therefor with rotating grinding tools; Accessories therefor
    • B24B23/028Angle tools
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B51/00Arrangements for automatic control of a series of individual steps in grinding a workpiece
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K11/00Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
    • H02K11/30Structural association with control circuits or drive circuits
    • H02K11/33Drive circuits, e.g. power electronics
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K7/00Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/14Structural association with mechanical loads, e.g. with hand-held machine tools or fans
    • H02K7/145Hand-held machine tool

Definitions

  • the present disclosure relates to a handheld electric work machine.
  • WO2017/051892 discloses a grinder with a side handle.
  • the side handle is attached to a housing accommodating a motor.
  • the kickback refers to a phenomenon that a tool mounted on the grinder receives a reaction force from a work target and thereby the grinder is swung around.
  • the grinder is configured to reduce occurrence the kickback.
  • the grinder is configured to drive the motor during the side handle being gripped by the user.
  • Whether the side handle is gripped is detected by a detecting unit provided on the side handle. Detection signals from the detecting unit are input to a controller arranged within a housing. The controller controls a driving of the motor.
  • One aspect of the present disclosure provides an electric work machine including a motor, a motor driver, an output shaft, a housing, two or more measurement devices, and a control circuit.
  • the motor generates a rotational force.
  • the motor driver supplies an electric power to the motor, thereby to drive the motor.
  • the output shaft transmits the rotational force of the motor to a tool, thereby to drive the tool.
  • the housing (i) includes a handle (or a side handle) fixed thereto or (ii) is configured such that the handle is detachably attached thereto.
  • the handle is gripped by a user of the handheld electric work machine.
  • Two or more measurement devices receive two or more loads from the handle fixed or attached to the housing, and also (ii) measure the two or more loads received.
  • the control circuit adjusts a magnitude of the electric power, based on the two or more loads measured.
  • the control circuit may determine whether the handle is gripped, based on the two or more loads measured.
  • the handle When the handle is fixed or attached to the housing, the handle abuts the housing. In this case, the two or more measurement devices receive substantially equal loads to each other.
  • the control circuit enables a detection (or confirmation, or grasping) of a state of the handle, based on the two or more loads.
  • the electric work machine eliminates the need for providing (i) the measurement device on the handle, and (ii) a signal path from the measurement device to the control circuit disposed within the housing. Thus, a configuration of the electric work machine can be simplified.
  • FIG. 1 is a perspective view of an electric work machine in an embodiment
  • FIG. 2 A is a schematic front view of a gear housing that is not mounted on a tool
  • FIG. 2 B is a schematic side view of the gear housing that is not mounted on the tool (a diagram of the electric work machine, as viewed from a left of the electric work machine);
  • FIG. 3 A is a perspective view of a handle
  • FIG. 3 B is a side view of the handle (with a transparent diagram of a shaft disposed within a holding portion);
  • FIG. 4 A is an explanatory diagram of the handle that is attached to the gear housing and is not gripped;
  • FIG. 4 B is an explanatory diagram of the handle that is attached to the gear housing and is gripped;
  • FIG. 5 is a block diagram of a configuration of a driving device
  • FIG. 6 is a flowchart of a connecting/gripping determination process
  • FIG. 7 is a flowchart of a motor control process
  • FIG. 8 is a flowchart of a modification example of a connecting/gripping determination process
  • FIG. 9 is a flowchart of a modification example of a motor control process.
  • FIG. 10 is a perspective view of an electric work machine in another embodiment.
  • One embodiment may provide a handheld electric work machine (hereinafter, an “electric work machine”) including at least any one of the following Features 1 through 7.
  • the handle may be fixed or attached to any portions of the housing.
  • the handle may be fixed or attached to the housing in any attaching manner.
  • the handle may be in any form, for example, a side handle. That is, the handle may be fixed to or detachably attached to a side surface of the housing.
  • the handle may be undetachable from the housing.
  • the housing may be configured to be gripped by the user. That is, user may use the electric work machine with gripping the handle in one hand and with the housing in the other hand.
  • the control circuit may determine whether the handle is attached to the housing and/or whether the handle is gripped by the user, based on the two or more loads measured.
  • the electric work machine including at least one of the Features 1 through 7 can detect the state of the handle with a simple configuration in the housing. Further, the magnitude of the electric power can be adjusted in accordance with the state of the handle.
  • One embodiment may include the following Feature 8 in addition to or in place of at least one of the aforementioned Features 1 through 7.
  • Each of the first and second magnitude is greater than zero.
  • the second magnitude may be zero.
  • the electric work machine including at least Feature 1 to 8 adjusts the magnitude of the electric power to the second magnitude, based on the two or more loads measured. Thus, occurrence of kickback is reduced.
  • One embodiment may include at least one of the following Features 9 through 11 in addition to or in place of at least one of the aforementioned Features 1 through 8.
  • the shaft may be undetachable from the first hole.
  • One embodiment may include the following Feature 12 and/or Feature 13 in addition to or in place of at least one of the aforementioned Features 1 through 11.
  • the electric work machine including at least Features 1 through 7, 12, and 13 can readily measure the two or more loads.
  • One embodiment may include at least one of the following Features 14 through 16 in addition to or in place of at least one of the aforementioned Features 1 through 13.
  • One embodiment may include the following Feature 17 in addition to or in place of at least one of the aforementioned Features 1 through 16.
  • One embodiment may include the following Feature 18 and/or Feature 19 in addition to or in place of at least one of the aforementioned Features 1 through 17.
  • the electric work machine including at least Features 1 through 7, and 17 through 19 can adjust the two or more loads from the handle (specifically, for example, the holding portion) with a corresponding one of the first elastic body. This achieves a protection of the two or more measurement devices from excessive loads, and also an adjustment of measurement sensitivity (or detection sensitivity) of the two or more measurement devices.
  • One embodiment may include the following Feature 20 in addition to or in place of at least one of the aforementioned Features 1 through 19.
  • the electric work machine including at least the Features 1 through 7, 9, and 20 enables a reduction in variability of the two or more loads caused by changes in a positional relationship (for example, a distance) between the two or more measurement devices and the handle.
  • One embodiment may include the following Feature 21 in addition to or in place of at least one of the aforementioned Features 1 through 20.
  • the electric work machine including at least the Features 1 through 7, 9, and 21 enables the second elastic body to absorb (or damp) vibrations transmitted from the housing to the handle. Accordingly, it is possible to reduce a transmission of the vibrations in the electric work machine to user's hand.
  • One embodiment may include the following Feature 22 and/or Feature 23 in addition to or in place of at least one of the aforementioned Features 1 through 21.
  • the electric work machine including at least the Features 1 through 7, 9, and 21 through 23 enables a reduction in variability of the two or more loads caused by vibrations in the electric work machine. Accordingly, the two or more loads can be more accurately measured, and this enables the magnitude of the electric power to be suitably controlled.
  • One embodiment may include the following Feature 24 in addition to or in place of at least one of the aforementioned Features 1 through 23.
  • the electric work machine including at least the Features 1 through 7, and 24, if the handle is not attached to the housing, enables a reduction in kickback by limiting the electric power to the motor.
  • the control circuit may adjust the magnitude of the electric power to the first magnitude. If at least one of the two or more loads measured is greater than or equal to the first threshold, the control circuit may determine that the handle is fixed or attached to the housing. When the control circuit determines that the handle is fixed or attached to the housing the control circuit may determine whether the handle is gripped by the user.
  • the control circuit may determine that the handle is not attached to the housing, based on none of the two or more loads measured by the two or more measurement devices has reached the first threshold.
  • One embodiment may include the following Feature 25 in addition to or in place of at least one of the aforementioned Features 1 through 24.
  • One embodiment may include the following Feature 26 in addition to or in place of at least one of the aforementioned Features 1 through 25.
  • the two or more loads are substantially equal to each other (for example, an initial load). Conversely, when the handle is gripped by the user, the two or more loads become unbalanced. Specifically, for example, at least one of the two or more loads become greater than the initial load.
  • the control circuit may determine that the handle is gripped by the user. If none of the two or more loads reaches the second threshold, the control circuit may determine that the handle is not gripped by the use.
  • One embodiment may include the following Feature 27 and/or Feature 28 in addition to or in place of at least one of the aforementioned Features 1 through 26.
  • the two or more loads may vary.
  • the control circuit may determine that the handle is gripped by the user.
  • Such electric work machine can more successfully detect that the handle is gripped by the user.
  • One embodiment may include the following Feature 29 and/or Feature 30 in addition to or in place of at least one of the aforementioned Features 1 through 28.
  • control circuit may determine that the tool is pressed against an external work target (or work piece).
  • the electric work machine including at least the Features 1 through 7, 24, 25, 29, and 30 enables a reduction in occurrence of kickback immediately after the start time of driving the motor.
  • One embodiment may include the following Feature 31 in addition to or in place of at least one of the aforementioned Features 1 through 30.
  • the user can relax such a pressing state, thereby to cancel the limitation of the electric power. Accordingly, a rotation speed of the motor can be increased from a rotation speed before the limitation. As a result, even if the electric power is limited at the start time of driving the motor, it is possible for the user to return the motor to a normal rotational state during an operation, thereby to perform a desired work.
  • One embodiment may include the following Feature 32 and/or Feature 33 in addition to or in place of at least one of the aforementioned Features 1 through 31.
  • the embodiment may further include the following Feature 34. Further/alternatively, if one embodiment includes the aforementioned Feature 33, the embodiment may further include the following Feature 35.
  • One embodiment may include at least one of the following Features 36 through 38 in addition to or in place of at least one of the aforementioned Features 1 through 35.
  • One embodiment may provide a method of controlling the motor in the electric work machine including at least any one of the following Features 39 and 40.
  • the method including the Features 39 and 40 can adjust the magnitude of the electric power in accordance with the state of the handle.
  • the aforementioned Features 1 through 40 may be combined in any way. In one embodiment, any of the aforementioned Features 1 through 40 may be omitted.
  • the present embodiment provides a handheld electric work machine (hereinafter, “electric work machine”) 1 .
  • the electric work machine 1 in the present embodiment is in a form of a handheld electric grinder.
  • the electric work machine 1 includes a main body (or housing) 2 .
  • the main body 2 includes a motor housing 4 , a gear housing 6 , and a rear housing 8 .
  • the electric work machine 1 includes a power cord 9 .
  • the main body 2 is configured such that a handle 50 is detachably attached thereto.
  • the motor housing 4 has a substantially cylindrical shape.
  • the motor housing 4 accommodates a motor 30 (see FIG. 5 ).
  • the motor 30 includes a rotor (not shown). Rotation of the motor 30 specifically means that the rotor rotates.
  • the motor 30 in the present embodiment is in a form of an AC motor.
  • the motor 30 is arranged in the motor housing 4 such that a rotation axis of the motor 30 (that is, a rotation axis of the rotor) is parallel or substantially parallel to a central axis of the motor housing 4 .
  • the central axis passes through the main body 2 (for example, the gravity center thereof or the vicinity of the gravity center), and extends in front-rear directions of the electric work machine 1 .
  • the motor 30 may be arranged such that the rotation axis coincides with or substantially coincides with the central axis.
  • the rotor protrudes frontward (that is, toward the gear housing 6 ).
  • the rear housing 8 has a substantially cylindrical shape.
  • the rear housing 8 is provided behind the motor housing 4 .
  • the rear housing 8 accommodates a driving device 10 (see FIG. 5 ).
  • the driving device 10 receives an electric power from an external AC power source via the power cord 9 .
  • the driving device 10 supplies the received electric power to the motor 30 , thereby to drive the motor 30 .
  • the rear housing 8 is configured such that a user of the electric work machine 1 may grip the rear housing 8 in one hand. That is, the rear housing 8 works as a grip.
  • a trigger 34 is provided on the rear housing 8 closer to the motor housing 4 . The user can move (or pull, or manually operate) the trigger 34 in one hand, while gripping the rear housing 8 in the same hand.
  • the gear housing 6 is provided in front of the motor housing 4 .
  • the gear housing 6 accommodates a drive mechanism 7 .
  • the drive mechanism 7 includes two or more gears.
  • the drive mechanism 7 ( i ) converts a rotational force of the motor 30 to a rotational force around a rotational axis of an output shaft (or the spindle) 22 (see FIG. 2 A and FIG. 2 B ), and (ii) transmits the converted rotational force to the output shaft 22 .
  • the gear housing 6 accommodates the output shaft 22 .
  • the output shaft 22 is accommodated such that a central axis (that is, the rotational axis) of the output shaft 22 is perpendicular to the rotation axis of the motor 30 .
  • the drive mechanism 7 includes, for example, two bevel gears. The two bevel gears transmit the rotation of the motor 30 to the output shaft 22 .
  • a distal end of the output shaft 22 protrudes from the gear housing 6 .
  • a tool 20 (see FIG. 1 ) is detachably attached to the distal end of the output shaft 22 .
  • the output shaft 22 receives the rotational force of the motor 30 via the drive mechanism 7 .
  • the output shaft 22 transmits the received rotational force to the tool 20 , thereby to rotate the tool 20 .
  • the output shaft 20 rotates integrally with the tool 20 .
  • the tool 20 may be, for example, disc-shaped.
  • the tool 20 attachable to the output shaft 22 includes, for example, a cutting blade (or an abrasive cut-off wheel).
  • the tool 20 is capable of grinding, cutting, or polishing a work target (or work piece).
  • the tool 20 may be in a form of, for example, a grinding wheel, a cutting wheel, or a wire brush.
  • a portion or all of the drive mechanism 7 may be omitted.
  • the drive mechanism 7 does not have to include a gear. That is, the rotational force of the motor 30 may be transmitted to the output shaft 22 not via a gear.
  • the motor 30 may be arranged such that the rotation axis of the motor 30 is parallel to the output shaft 22 . In this case, the rotor of the motor 30 may be directly coupled to the output shaft 22 .
  • a wheel cover 24 is attached to the gear housing 6 .
  • broken pieces of the work target and/or the tool 20 may scatter in a surrounding area of the electric work machine 1 .
  • the wheel cover 24 protects the user from such broken pieces.
  • the wheel cover 24 has a substantially semi-circular shape.
  • the wheel cover 24 covers, from the gear housing 6 , a portion (a substantially half, in the present embodiment) of the tool 20 fixed to the output shaft 22 .
  • the wheel cover 24 is detachably attached to a cover attachment portion provided on a distal end portion of the gear housing 6 .
  • the distal end portion of the gear housing 6 protrudes from the output shaft 22 .
  • the cover attachment portion has a cylindrical shape, and surrounds the output shaft 22 .
  • a central axis of the cover attachment portion coincides with the central axis of the output shaft 22 .
  • the gear housing 6 includes a first side surface 6 a and a second side surface 6 b .
  • the first side surface 6 a corresponds to a left face of the gear housing 6
  • the second side surface 6 b corresponds to a right face of the gear housing 6 .
  • a first attachment portion 42 L is provided on the first side surface 6 a .
  • a second attachment portion 42 R is provided on the second side surface 6 b .
  • the handle 50 is detachably attached to the first attachment portion 42 L or the second attachment portion 42 R. That is, the handle 50 in the present embodiment is attached to a side surface of the main body 2 .
  • the handle 50 is referred as a “side handle 50 ”.
  • the first attachment portion 42 L includes a first receiver 421 L.
  • the first receiver 421 L has a tubular (for example, cylindrical) shape. That is, the first receiver 421 L includes a first through hole 43 L.
  • the second attachment portion 42 R includes a second receiver 421 R.
  • the second receiver 421 R has a tubular (for example, cylindrical) shape. That is, the second receiver 421 R includes a second through hole 43 R.
  • the first and second receivers 421 L, 421 R each include a first end surface and a second end surface.
  • each of the first end surface faces the gear housing 6 , and abuts a corresponding side surface of the gear housing 6 .
  • the second end surfaces correspond to the respective faces opposite to the first end surfaces.
  • Each of the second end surfaces has a planar shape.
  • a distance between the first end surface and the second end surface is constant in the present embodiment. In other words, in the present embodiment, a distance between the first side surface 6 a and the second end surface of the first receiver 421 L is constant, and a distance between the second side surface 6 b of and the second end surface of the second receiver 421 R is also constant.
  • Each of the second end surfaces of the first and second receivers 421 L, 421 R is parallel to the rotation axis of the motor 30 .
  • the first attachment portion 42 L further includes a first attachment hole 40 L.
  • the first attachment hole 40 L includes a first opening 40 La.
  • the first attachment hole 40 L is formed on the first side surface 6 a of the gear housing 6 .
  • the side handle 50 includes a shaft 60 (see FIG. 3 A ). The shaft 60 is screwed in the first attachment hole 40 L. A central axis of the first attachment hole 40 L coincides with a central axis of the first through hole 43 L.
  • the second attachment portion 42 R further includes a second attachment hole 40 R.
  • the second attachment hole 40 R includes a second opening 40 Ra.
  • the second attachment hole 40 R is formed on the second side surface 6 b of the gear housing 6 .
  • the shaft 60 is screwed in the second attachment hole 40 R.
  • the central axis of the second attachment hole 40 R coincides with a central axis of second through hole 43 R.
  • the shaft 60 is selectively screwed in the first attachment hole 40 L or the second attachment hole 40 R.
  • the side handle 50 includes the shaft 60 and a holding portion 52 .
  • the shaft 60 corresponds to an axial center of the side handle 50 .
  • a screw part 62 is formed at a first edge part of the shaft 60 .
  • the screw part 62 is in a form of, for example, a male screw.
  • the holding portion 52 is gripped by the user.
  • FIG. 3 B an inside of the holding portion 52 is transparently illustrated.
  • the holding portion 52 includes an insertion hole 57 .
  • the second end of the shaft 60 is inserted in the insertion hole 57 , so that the shaft 60 is fixed to the holding portion 52 .
  • a vibration proof rubber 58 is arranged on an inner surface of the insertion hole 57 .
  • the vibration proof rubber 58 has a first stiffness (or a first spring constant).
  • the shaft 60 abuts the vibration proof rubber 58 . That is, the shaft 60 is fixed to the holding portion 52 via the vibration proof rubber 58 .
  • a first edge part side including the screw part 62 protrudes from the holding portion 52 .
  • Each of the first and second attachment holes 40 L, 40 R includes a screw thread formed on its inner circumferential surface. Accordingly, the first and second attachment holes 40 L, 40 R each works as a female screw. That is, the first and second attachment holes 40 L, 40 R may be screwed on the screw part 62 of the side handle 50 .
  • the screw part 62 of the side handle 50 is screwed on the first attachment hole 40 L, and thus the side handle 50 is fixed to the first attachment portion 42 L (and hence, fixed to the gear housing 6 ).
  • the screw part 62 of the side handle 50 is screwed on the second attachment hole 40 R, and thus the side handle 50 is fixed to the second attachment portion 42 R (i.e., the gear housing 6 ).
  • the user can selectively attach the side handle 50 to the first attachment portion 42 L or the second attachment portion 42 R.
  • the side handle 50 can operate the electric work machine 1 while gripping the rear housing 8 in, for example, his/her right hand and also gripping the side handle 50 in his/her left hand.
  • the side handle 50 is attached to the second attachment portion 42 R, the user can operate the electric work machine 1 while gripping the rear housing 8 , for example, in the left hand and also gripping the side handle 50 in the right hand.
  • the side handle 50 further includes a collar portion (or a flange) 54 .
  • the collar portion 54 is provided to the first edge of the holding portion 52 .
  • the first edge part of the shaft 60 protrudes from the first edge of the holding portion 52 .
  • the first end face of the collar portion 54 includes an abutment portion 56 .
  • the abutment portion 56 has an annular shape.
  • the shaft 60 passes through the abutment portion 56 .
  • a central axis of the abutment portion 56 coincides with the central axis of the shaft 60 .
  • a first end surface of the abutment portion 56 is perpendicular to the central axis of the shaft 60 .
  • the first end surface of the abutment portion 56 faces and abuts the first attachment portion 42 L or the second attachment portion 42 R.
  • the first end surface of the abutment portion 56 corresponds to one example of the second surface described in the Overview of Embodiments.
  • the second end surface of the abutment portion 56 faces and abuts the first end face of the collar portion 54 .
  • two or more measurement devices are provided on the first attachment portion 42 L.
  • the two or more measurement devices in the present embodiment include a first measurement device 441 , a second measurement device 442 , and a third measurement device 443 .
  • the first through third measurement devices 441 through 443 are provided on the second end surface of the first receiver 421 L. If the side handle 50 is attached to the first attachment portion 42 L, the first through third measurement devices 441 through 443 respectively receive first through third loads from the abutment portion 56 of the side handle 50 .
  • the first measurement device 441 measures (or detects) the first load
  • the second measurement device 442 measures the second load
  • the third measurement device 443 measures the third load.
  • each of the first through third measurement devices 441 through 443 is in a form of a resistive pressure sensor.
  • the resistive pressure sensor includes a resistor.
  • the resistor has a variable resistance value. That is, the resistance value of the resistor varies depending on loads applied by the resistive pressure sensor.
  • the first through third measurement devices 441 through 443 are provided on the second end surface of the first receiver 421 L. Specifically, the first through third measurement devices 441 through 443 are arranged along the first through hole 43 L (or along the first opening 40 La).
  • the first through third measurement devices 441 through 443 are spaced from each other at a certain distance (specifically, by an angle of 120 degrees) along a circumferential direction of the second end surface having an annular shape, of the first receiver 421 L. Further, each of the first through third measurement devices 441 through 443 has an equal distance from the central axis of the first attachment hole 40 L. In other words, the first through third measurement devices 441 through 443 are arranged on a circumference of a circular whose center is the central axis of the first attachment hole 40 L, and also such that the circular is perpendicular to the central axis of the first attachment hole 40 L.
  • the first through third measurement devices 441 through 443 respectively includes first through third rubbers 461 through 463 .
  • the first measurement device 441 includes a first pressure-receiving surface 441 a . If the side handle 50 is attached to the first attachment portion 42 L, the first pressure-receiving surface 441 a faces the abutment portion 56 of the side handle 50 , and receives the first load from the abutment portion 56 .
  • the first rubber 461 is provided on the first pressure-receiving surface 441 a . Accordingly, the first measurement device 441 receives the first load via the first rubber 461 .
  • the second measurement device 442 includes a second pressure-receiving surface 442 a .
  • the second pressure-receiving surface 442 a faces the abutment portion 56 of the side handle 50 , and receives the second load from the abutment portion 56 .
  • the second rubber 462 is provided on the second pressure-receiving surface 442 a . Accordingly, the second measurement device 442 receives the second load via the second rubber 462 .
  • the third measurement device 443 includes a third pressure-receiving surface 443 a . If the side handle 50 is attached to the first attachment portion 42 L, the third pressure-receiving surface 443 a faces the abutment portion 56 of the side handle 50 , and receives the third load from the abutment portion 56 .
  • the third rubber 463 is provided on the third pressure-receiving surface 443 a . Accordingly, the third measurement device 443 receives the third load via the third rubber 463 .
  • the second attachment portion 42 R also includes two or more measurement devices.
  • the second attachment portion 42 R includes a fourth measurement device 444 , a fifth measurement device 445 , and a sixth measurement device 446 .
  • the fourth through sixth measurement devices 444 through 446 are provided on the second end surface of the second receiver 421 R. If the side handle 50 is attached to the second attachment portion 42 R, the fourth through sixth measurement devices 444 through 446 respectively receive fourth through sixth loads from the abutment portion 56 of the side handle 50 .
  • the fourth measurement device 444 measures (or detects) the fourth load
  • the fifth measurement device 445 measures the fifth load
  • the sixth measurement device 446 measures the sixth load.
  • each of the fourth through sixth measurement devices 444 through 446 is in a form of the resistive pressure sensor.
  • the fourth through sixth measurement devices 444 through 446 are provided on the second end surface of the second receiver 421 R.
  • the fourth through sixth measurement devices 444 through 446 are arranged along the second through hole 43 R (or along the second opening 40 Ra). More Specifically, the fourth through sixth measurement devices 444 through 446 are spaced from each other at a certain distance (specifically, by an angle of 120 degrees) along a circumferential direction of the second end surface having an annular shape, of the second receiver 421 R. Further, each of the fourth through sixth measurement devices 444 through 446 has an equal distance from the central axis of the second attachment hole 40 R.
  • the fourth through sixth measurement devices 444 through 446 are arranged on a circumference of a circular whose center is the central axis of the second attachment hole 40 R, and also such that the circular is perpendicular to the central axis of the second attachment hole 40 R.
  • the fourth through sixth measurement devices 444 through 446 respectively include fourth through sixth rubbers 464 through 466 .
  • the fourth measurement device 444 includes a fourth pressure-receiving surface 444 a . If the side handle 50 is attached to the second attachment portion 42 R, the fourth pressure-receiving surface 444 a faces the abutment portion 56 of the side handle 50 , and receives the fourth load from the abutment portion 56 .
  • the fourth rubber 464 is provided on the fourth pressure-receiving surface 444 a . Accordingly, the fourth measurement device 444 receives the fourth load via the fourth rubber.
  • the fifth measurement device 445 includes a fifth pressure-receiving surface 445 a .
  • the fifth pressure-receiving surface 445 a faces the abutment portion 56 of the side handle 50 , and receives the fifth load from the abutment portion 56 .
  • the fifth rubber 465 is provided on the fifth pressure-receiving surface 445 a . Accordingly, the fifth measurement device 445 receives the fifth load via the fifth rubber 465 .
  • the sixth measurement device 446 includes a sixth pressure-receiving surface 446 a . If the side handle 50 is attached to the second attachment portion 42 R, the sixth pressure-receiving surface 446 a faces the abutment portion 56 of the side handle 50 , and receives the sixth load from the abutment portion 56 .
  • the sixth rubber 466 is provided on the sixth pressure-receiving surface 446 a . Accordingly, the sixth measurement device 446 receives the sixth load via the sixth rubber 466 .
  • respective magnitudes of the fourth through sixth loads (for example, an initial value F1) received by the fourth through sixth measurement devices 444 through 446 are substantially equal to each other.
  • the holding portion 52 in the side handle 50 may be tilted with respect to the shaft 60 , as shown in FIG. 4 B .
  • Such tilting is caused by, for example, a holding force of the user, a self-weight of the electric work machine 1 , or the like.
  • the first through the sixth rubbers 461 through 466 each have a second stiffness (or a second spring constant).
  • the second stiffness is smaller than the first stiffness of the vibration proof rubber 58 .
  • the vibration proof rubber 58 is more rigid than each of the first through sixth rubbers 461 through 466 .
  • the holding portion 52 is supported by the vibration proof rubber 58 . Accordingly, the first stiffness of the vibration proof rubber 58 is adjusted, and thereby any tilt of the holding portion when the side handle 50 is gripped can be set (or adjusted).
  • the fourth through sixth loads apply to the fourth through sixth measurement devices 444 through 446 from the abutment portion 56 of the side handle 50 are unbalanced.
  • any one or two magnitudes of the fourth through sixth loads reaches a value F2 greater than the initial value F1, one or two of the other magnitudes reaches a value F3 smaller than the initial value F1.
  • the fourth through sixth loads are adjustable by adjusting the respective second stiffnesses of the fourth through sixth rubbers 464 through 466 .
  • the driving device 10 accommodated in the rear housing 8 includes a driving system 12 and a control system 14 .
  • the driving system 12 is configured to receive an AC power from the external AC power source of the electric work machine 1 , thereby to drive the motor 30 with the AC power.
  • the control system 14 is configured to control driving of the motor 30 .
  • the driving system 12 includes the motor 30 , a motor driver 36 , and a trigger switch 35 .
  • the trigger switch 35 is switched between an ON-state and an OFF-state in conjunction with the trigger 34 . Specifically, when the trigger 34 is not moved (that is, not manually operated), the trigger switch 35 is in the OFF-state. When the trigger 34 is moved, the trigger switch 35 is in the ON-state. When the trigger switch 35 is in the ON-state, the AC power is supplied to the motor driver 36 through a power cord 9 via the trigger switch 35 .
  • the motor driver 36 supplies the AC power to the motor 30 , thereby to drive the motor 30 .
  • the motor driver 36 in the present embodiment includes a bidirectional thyristor. By turning ON or OFF the bidirectional thyristor, the AC power (hereinafter, a “driving power”) to be supplied to the motor 30 is controlled (or adjusted).
  • the control system 14 includes a control circuit 80 .
  • the control circuit 80 in the present embodiment is in a form of a microcomputer or a microcontroller unit (MCU), including, for example, a CPU 80 a and a memory 80 b .
  • the memory 80 b may include a semiconductor memory, such as a ROM, a RAM, a NVRAM (non-volatile random-access memory), or a flash memory. That is, the control circuit 80 in the present embodiment includes a microcomputer.
  • the control circuit 80 executes a program stored in a non-transitory tangible storage medium, to thereby achieve various functions of the control circuit 80 .
  • the memory 80 b corresponds to the non-transitory tangible storage medium including programs stored therein.
  • the memory 80 b stores programs related to a connecting/gripping determination process (see FIG. 6 ) and a motor control process (see FIG. 7 ), will be described below.
  • control circuit 80 may be achieved by execution of the program (that is, software processing), or by one or more hardware elements.
  • the control circuit 80 may include a combination of various individual electrical components instead of a microcomputer or in addition to a microcomputer, or may include an Application Specified Integrated Circuit (ASIC), an Application Specific Standard Product (ASSP).
  • ASIC Application Specified Integrated Circuit
  • ASSP Application Specific Standard Product
  • the control circuit 80 may include a programmable logic device that can configure any logic circuit. Examples of the programmable logic device include Field Programmable Gate Array (FPGA).
  • the control circuit 80 may be in a form of a hard wired circuit.
  • the control circuit 80 receives a first detection signal from the first measurement device 441 , a second detection signal from the second measurement device 442 , a third detection signal from the third measurement device 443 , a fourth detection signal from the fourth measurement device 444 , a fifth detection signal from the fifth measurement device 445 , and a sixth detection signal from the sixth measurement device 446 .
  • the first through sixth detection signals respectively indicate the magnitudes of the first through sixth loads received (i.e., measured) by the first through sixth measurement devices 441 through 446 .
  • the control circuit 80 determines, based on the magnitudes of the first through sixth loads indicated by the first through sixth detection signals received, whether the side handle 50 is attached to the first attachment portion 42 L or the second attachment portion 42 R. If the side handle 50 is attached to the attachment portion 42 L or the second attachment portion 42 R, the control circuit 80 further determines whether the side handle 50 is gripped by the user. This determination is made based on the magnitudes of the first through sixth loads indicated by the first through sixth detection signals.
  • the control circuit 80 controls (or adjusts) the magnitude of the driving power to the motor 30 . Specifically, the control circuit 80 controls the magnitude of the driving power to the motor 30 , based on the magnitudes of the measured first through sixth loads.
  • the control circuit 80 supplies a first magnitude (or a normal magnitude) of a driving power (hereinafter, “normal driving power”) from the motor driver 36 to the motor 30 , in response to the trigger 34 being moved.
  • the first magnitude of the normal driving power is greater than zero.
  • the first magnitude of the normal driving power may be, for example, a preset constant magnitude Wu. Further, for example, the first magnitude of the normal driving power may vary up to a maximum value WuX, in accordance with a position of the trigger 34 .
  • the control circuit 80 limits a supply of the driving power to the motor 30 . That is, the control circuit 80 supplies a second magnitude of the electric power (hereinafter, a “limited driving power”) from the motor driver 36 to the motor 30 .
  • the second magnitude is smaller than the first magnitude.
  • the second magnitude is greater than zero.
  • the second magnitude may be zero.
  • the control circuit 80 limits the supply of the driving power to the motor 30 . That is, if the side handle 50 is not gripped by the user, the control circuit 80 supplies a limited magnitude of the electric power from the motor driver 36 to the motor 30 .
  • the limited magnitude is smaller than the magnitude of the normal driving power.
  • the above-described limited driving power is supplied to the motor 30 . Accordingly, also in this case, the rotation speed of the motor 30 is decreased. In this case, the magnitude of the limited driving power may be distinct from that when the side handle 50 is not attached.
  • the normal driving power is supplied to the motor 30 .
  • the user In order for the user to drive the motor 30 while gripping the side handle 50 , the user usually is required to grip the electric work machine 1 with both hands.
  • the electric work machine 1 in the present embodiment is configured to allow the normal driving power to be supplied to the motor 30 only when the user grips the rear housing 8 and the side handle 50 are gripped with both hands.
  • the side handle 50 is not attached to the main body 2 , the supply of the driving power to the motor 30 is limited. If (i) the side handle 50 is attached to the main body 2 , and also (ii) the side handle 50 is not gripped by the user, the supply of the driving power to the motor 30 is limited. This inhibits occurrence of a kickback.
  • the driving device 10 includes an AC/DC converter 82 .
  • the AC/DC converter 82 receives the AC power from the power cord 9 .
  • the AC/DC converter 82 generates a DC power-supply voltage Vdc from the received AC power.
  • the power-supply voltage Vdc is supplied to each of components (for example, the control circuit 80 , first and second sensor circuits 70 L, 70 R, which are described below) of the control system 14 , thereby to operate each component.
  • the AC/DC converter 82 in the present embodiment is in a form of an isolated converter. That is, the AC/DC converter 82 is electrically connected to the driving system 12 and the control system 14 . Specifically, the AC/DC converter 82 is electrically connected to (i) an AC power-supply line in the driving system 12 and (ii) a DC power-supply line in the control system 14 .
  • the AC power-supply line supplies the AC power from the power cord 9 to the motor driver 36 .
  • the DC power-supply line supplies the power-supply voltage Vdc to each component of the control system 14 .
  • the driving system 12 and the control system 14 are electrically isolated from each other within the AC/DC converter 82 . That is, the AC power-supply line and the DC power-supply line are electrically isolated from each other.
  • the AC/DC converter 82 may include, for example, a transformer (not shown), and magnetically couple the driving system 12 and the control system 14 via the transformer.
  • the control system 14 further includes a first sensor circuit 70 L and a second sensor circuit 70 R.
  • Each of the first and second sensor circuits 70 L, 70 R receive the power-supply voltage Vdc from the AC/DC converter 82 , thereby to operate.
  • the first sensor circuit 70 L (i) drives the first through third measurement devices 441 through 443 , and (ii) outputs the first through third detection signals.
  • the second sensor circuit 70 R (i) drives the fourth through sixth measurement devices 444 through 446 , and (ii) outputs the fourth through sixth detection signals.
  • the driving device 10 further includes a first optocoupler (or a first photocoupler, or a first opto-isolator, or a first optical isolator) 84 , a second optocoupler (or a second photocoupler, or a second opto-isolator, or a second optical isolator) 86 , and a third optocoupler (or a third photocoupler, or a third opto-isolator, or a third optical isolator) 88 .
  • a first optocoupler or a first photocoupler, or a first opto-isolator, or a first optical isolator
  • a second optocoupler or a second photocoupler, or a second opto-isolator, or a second optical isolator
  • a third optocoupler or a third photocoupler, or a third opto-isolator, or a third optical isolator
  • the first optocoupler 84 is coupled to the AC power-supply line in the driving system 12 . Specifically, the first optocoupler 84 is disposed between the trigger switch 35 and the motor driver 36 in the AC power-supply line. The first optocoupler 84 is further coupled to the control circuit 80 . However, the driving system 12 and the control system 14 are electrically isolated from each other within the first optocoupler 84 . The first optocoupler 84 optically couples, for example, the driving system 12 and the control system 14 .
  • the first optocoupler 84 outputs a trigger operation signal to the control circuit 80 .
  • the trigger operation signal indicates a state of the trigger switch 35 , that is, whether the trigger switch 35 is in the ON-state or the OFF-state (and thus, whether the trigger 34 is moved).
  • the trigger operation signal indicating the ON-state of the trigger switch 35 directs the control circuit 80 to drive the motor 30 .
  • the trigger operation signal indicating the ON-state of the trigger switch 35 corresponds to one example of the drive command in the Overview of Embodiments.
  • the second optocoupler 86 is coupled to the control circuit 80 and the motor driver 36 .
  • the driving system 12 and the control system 14 are electrically isolated from each other within the second optocoupler 86 .
  • the control circuit 80 and the motor driver 36 are electrically isolated from each other within the second optocoupler 86 .
  • the second optocoupler 86 optically couples, for example, the driving system 12 and the control system 14 .
  • the second optocoupler 86 receives a permission signal from the control circuit 80 , the permission signal is transmitted to the motor driver 36 .
  • the permission signal permits the motor driver 36 to drive the motor 30 .
  • the third optocoupler 88 is coupled to the control circuit 80 and the motor driver 36 . However, the driving system 12 and the control system 14 are electrically isolated from each other within the third optocoupler 88 .
  • the third optocoupler 88 optically couples, for example, the driving system 12 and the control system 14 .
  • the command signal is transmitted to the motor driver 36 .
  • the command signal commands (or directs) the motor driver 36 to supply the driving power required for the motor 30 .
  • the command signal commands the motor driver 36 to supply the normal driving power or the limited driving power.
  • Each of the first through third optocouplers 84 , 86 , 88 may be couple the driving system 12 to the control system 14 in any manner, other than in an electrically coupling manner.
  • Each of the first through third optocouplers 84 , 86 , 88 may, for example, electromagnetically couple the driving system 12 to the control system 14 .
  • the driving system 12 and the control system 14 are electrically isolated completely (or almost completely) each other. This inhibits the AC power conducted (or transmitted) in the driving system 12 from affecting operation of the control system 14 (for example, a malfunction of the control system 14 ).
  • the control system 14 further includes a first LED 72 , a second LED 74 , and a third LED 76 .
  • the first through third LEDs 72 , 74 , 76 are coupled to the control circuit 80 .
  • the first LED 72 is illuminated when the control circuit 80 determines that the side handle 50 is attached to the gear housing 6 .
  • the second LED 74 is illuminated when the control circuit 80 determines that the side handle 50 is gripped.
  • the third LED 76 is illuminated, for example, when the trigger switch 35 is in the ON-state.
  • the connecting/gripping determination process is executed to determine whether the side handle 50 is gripped.
  • the motor control process is executed to drive the motor 30 in accordance with the state of the trigger switch 35 .
  • the control circuit 80 specifically, CPU 80 a
  • the connecting/gripping determination process and the motor control process are executed.
  • the connecting/gripping determination process and the motor control process are each executed when the programs, stored in the memory 80 b and correspond to the processes, are executed.
  • the connecting/gripping determination process is repeatedly executed, for example, periodically.
  • the connecting/gripping determination process and the motor control process include a main routine executed by the control circuit 80 in the present embodiment.
  • the control circuit 80 starts the connecting/gripping determination process, and, in S 110 , acquires the first through sixth loads. Specifically, the control circuit 80 acquires the first through sixth loads measured by the first through sixth measurement devices 441 through 446 . More specifically, the control circuit 80 receives the first through sixth detection signals from the first through sixth measurement devices 441 through 446 . The control circuit 80 acquires the first through sixth loads measured (hereinafter, collectively referred to as a “measured loads”), based on the first through sixth detection signals received.
  • the control circuit 80 determines whether at least one of the measured loads acquired in S 110 is greater than or equal to a first threshold LT 1 .
  • the first threshold LT 1 may be, for example, preset.
  • the control circuit 80 determines that the side handle 50 is attached to the first attachment portion 42 L. If at least one of the acquired fourth through sixth loads is greater than or equal to the first threshold LT 1 , the control circuit 80 determines that the side handle 50 is attached to the second attachment portion 42 R.
  • control circuit 80 determines that the side handle 50 is not attached to the gear housing 6 .
  • control circuit 80 proceeds to S 130 .
  • the control circuit 80 lets the first LED 72 light off.
  • the control circuit 80 lets the second LED 74 light off.
  • the control circuit 80 sets an electric power limit flag. After S 150 , the control circuit 80 ends the connecting/gripping determination process.
  • control circuit 80 proceeds to S 160 .
  • the control circuit 80 lights the first LED 72 , thereby to notify the user that the side handle 50 is attached.
  • the control circuit 80 determines whether at least one of the measured loads acquired in S 110 is greater than or equal to a second threshold LT 2 .
  • the second threshold LT 2 may be, for example, preset.
  • the second threshold LT 2 is used to determine whether the side handle 50 attached to the first attachment portion 42 L or the second attachment portion 42 R is gripped by the user.
  • the second threshold LT 2 is greater than the first threshold LT 1 .
  • the control circuit 80 determines that the side handle 50 attached to the first attachment portion 42 L is gripped by the user. If at least one of the acquired fourth through sixth loads is greater than or equal to the second threshold LT 2 , the control circuit 80 determines that the side handle 50 attached to the second attachment portion 42 R is gripped by the user.
  • the control circuit 80 lights the second LED 74 in S 180 , thereby to notify the user that the user grips the side handle 50 .
  • control circuit 80 clears the electric power limit flag, on the basis that the side handle 50 is gripped. After S 190 , the control circuit 80 ends the connecting/gripping determination process.
  • the control circuit 80 determines whether at least one of the measured loads acquired has varied in a preset period of time (or is varying). For example, every time the connecting/gripping determination process is executed periodically, the acquired first through sixth loads may be stored. Further, by referring to the most recent two or more values stored in the preset period of time, a determination may be made whether each of the first through sixth loads varies or is kept. Alternatively, in S 200 , for example, wait for the preset period of time, and a determination is made whether on each of the first through sixth loads varies during that preset period of time.
  • the control circuit 80 determines that the user grips the side handle 50 . In this case, the control circuit 80 proceeds to S 180 .
  • control circuit 80 determines that the user does not grip the side handle 50 . In this case, the control circuit 80 proceeds to S 140 .
  • the electric power limit flag is cleared.
  • the electric power limit flag is set. Further, when the side handle 50 is attached to the attachment portion 42 L or the second attachment portion 42 R and the side handle 50 is not gripped by the user, the electric power limit flag is set.
  • the control circuit 80 starts the motor control process, and, in S 310 , determines whether the trigger switch 35 is in the ON-state. If the trigger switch 35 is not in the ON-state, the control circuit 80 repeats the process of S 310 .
  • the process proceeds to S 340 .
  • the control circuit 80 limits the supply of the driving power to the motor 30 . That is, the motor driver 36 is controlled so as to supply the limited driving power to the motor 30 . Specifically, the control circuit 80 outputs, to the motor driver 36 , the command signal commanding a limitation of the driving power via the third optocoupler 88 . Accordingly, the driving power (limited driving power) from the motor driver 36 , which is a decreased (limited) driving power at a normal time (i.e., the normal driving power), is supplied to the motor 30 , so that the motor 30 is driven.
  • the process proceeds to S 310 .
  • the process proceeds to S 330 .
  • the control circuit 80 does not limit the supply of the driving power to the motor 30 . That is, the motor driver 36 is controlled so as to supply the normal driving power to the motor 30 . If the process proceeds to S 330 in the state where the limited driving power is supplied, the control circuit 80 switches a supply power to the normal driving power. The control circuit 80 outputs to the motor driver 36 , via the third optocoupler 88 , the command signal commanding, specifically, that the driving power is not limited (or the limitation is canceled). This causes the normal driving power to be supplied from the motor driver 36 to the motor 30 , thereby to drive the motor 30 . After S 330 , the process proceeds to S 310 .
  • the side handle 50 is selectively attachable to the first attachment portion 42 L or the second attachment portion 42 R.
  • the first through third measurement devices 441 through 443 are provided on the first attachment portion 42 L.
  • the fourth through sixth measurement devices 444 through 446 are provided on the second attachment portion 42 R.
  • the first through sixth measurement devices 441 through 446 measure (or detect) the first through sixth loads, respectively.
  • the control circuit 80 determines, based on the measured first through sixth loads, whether the side handle 50 is attached to the first attachment portion 42 L or the second attachment portion 42 R. If the side handle 50 is attached to the first attachment portion 42 L or the second attachment portion 42 R, the control circuit 80 further determines whether the user grips the side handle 50 . In the present embodiment, the control circuit 80 holds such determination results by using the electric power limit flag.
  • the control circuit 80 determines whether the electric power limit flag is set. This determination indirectly corresponds to the determination whether the side handle 50 is gripped. If the electric power limit flag is not set (that is, the side handle 50 is gripped), the control circuit 80 drives the motor 30 at the normal driving power. On the other hand, if the electric power limit flag is set (that is, the side handle 50 is not gripped), the control circuit 80 drives the motor 30 at the limited driving power. In other words, the driving power to the motor 30 is decreased, compared with that at the normal times.
  • the electric work machine 1 in the present embodiment enables the control circuit 80 to determine whether the side handle 50 is gripped, without providing a detection unit (for example, a sensor) on the side handle 50 . Accordingly, the electric work machine 1 in the present embodiment readily achieves a simpler device configuration, compared with one described in Patent Document 1.
  • Each of the first and second attachment holes 40 L, 40 R corresponds to one example of the first hole in the Overview of Embodiments.
  • the vibration proof rubber 58 corresponds to one example of a second elastic body in the Overview of Embodiments.
  • Each of the first through the sixth rubbers 461 through 466 corresponds to one example of a first elastic body in the Overview of Embodiments.
  • Each of the first through the sixth pressure-receiving surface 441 a through 446 a corresponds to one example of a first surface in the Overview of Embodiments.
  • the driving system 12 corresponds to one example of a first electric system in the Overview of Embodiments.
  • the control system 14 corresponds to one example of a second electric system in the Overview of Embodiments.
  • the determinations are made on whether the side handle 50 is attached to the gear housing 6 , and whether the side handle 50 is gripped by the user.
  • the driving power is controlled to the normal driving power or the limited driving power.
  • the driving of the motor 30 may be started with the tool 20 being pressed against the work target.
  • the tool 20 may receive a reaction force from the work target, and thereby kickback may occur.
  • control circuit 80 may include a pressing-determination function.
  • the pressing-determination function includes determining, based on the acquired first through sixth loads, whether the tool 20 is pressed against the work target.
  • the connecting/gripping determination process and the motor control process that include the pressing-determination function is described by reference to FIG. 8 and FIG. 9 .
  • the connecting/gripping determination process shown in FIG. 8 corresponds to one of modifications of the connecting/gripping determination process shown in FIG. 6 .
  • steps of the process identical to those in FIG. 6 are denoted by the reference numerals used in FIG. 6 .
  • the motor control process shown in FIG. 9 corresponds to one of modifications of the motor control process shown in FIG. 7 .
  • steps of the process identical to those in FIG. 7 are denoted by the reference numerals used in FIG. 7 .
  • the control circuit 80 determines whether at least one of the measured loads acquired in S 110 is greater than or equal to a third threshold LT 3 .
  • the third threshold LT 3 may be, for example, preset.
  • the third threshold LT 3 is used to detect that the tool 20 is pressed against the work target. Thus, the third threshold LT 3 is greater than the second threshold LT 2 .
  • the control circuit 80 determines that the tool 20 is pressed against the work target. In this case, the control circuit 80 lights the third LED 76 in S 220 . Accordingly, it is notified that the tool 20 is pressed against the work target. Subsequently, in S 230 , the control circuit 80 sets a pressing flag. After S 230 , the control circuit 80 ends the connecting/gripping determination process.
  • control circuit 80 In S 210 , if all the measured loads acquired do not reach the third threshold LT 3 , the control circuit 80 lets the third LED 76 light off in S 240 . Subsequently, in S 250 , the control circuit 80 clears the pressing flag. After S 250 , the control circuit 80 ends the connecting/gripping determination process.
  • the control circuit 80 determines in S 314 whether the pressing flag is set. If the pressing flag is set, the process proceeds to S 318 .
  • the process proceeds to S 316 . If the pressing flag is not set in S 314 , this indicates that the trigger 34 is moved with the tool 20 not being pressed against the work target. Accordingly, in this case, the control circuit 80 clears the immediately-after-start flag in S 316 , then the process proceeds to S 318 .
  • the control circuit 80 determines in S 318 whether the immediately-after-start flag is set. If the immediately-after-start flag is set, the process proceeds to S 340 . If setting of the immediately-after-start flag is made in S 318 , this indicates that the trigger 34 is moved with the tool 20 being pressed against the work target. In other words, this indicates that the driving of the motor 30 is started with the tool 20 being pressed against the work target. Accordingly, in this case, the control circuit 80 supplies the limited driving power to the motor in S 340 , similar to S 150 .
  • Steps following S 320 are identical to those described in FIG. 7 .
  • the electric work machine 1 configured to execute the process steps described in FIG. 8 and FIG. 9 provides further effects described below, in addition to effects of the aforementioned embodiments. That is, the electric work machine 1 enables a reduction in a kickback that may result from that the driving of the motor 30 is started with the tool 20 being pressed against the work target.
  • the motor 30 If the driving of the motor 30 is started with the tool 20 being pressed against the work target, the motor 30 is driven with the limited driving power. If pressing of the tool 20 against the work target is released after the motor 30 is driven, the limitation of the driving power is canceled, and then the normal driving power is supplied to the motor 30 .
  • the rotation speed of the motor 30 is not increased because of pressing the tool 20 against the work target, the user can relax the pressing of the tool 20 against the work target, thereby to allow the normal driving power to be supplied to the motor 30 . As a result, the rotation speed of the motor 30 can be increased.
  • the first through sixth measurement devices 441 through 446 in the aforementioned embodiments is in the form of a resistive pressure sensor.
  • the first through sixth measurement devices 441 through 446 are not limited to the form of the resistive pressure sensor.
  • the first through sixth measurement devices 441 through 446 may be in a form of a sensitive rubber or a strain gauge.
  • the first through sixth measurement devices 441 through 446 may be in any form that can detect a load applied from the side handle 50 .
  • each of the first and second attachment portions 42 L, 42 R may include more than three measurement devices, or two measurement devices.
  • the electric work machine 1 in the aforementioned embodiments detects whether the side handle 50 is gripped, by utilizing a structure that the holding portion 52 is displaced (specifically, tilted as described above) with respect to the shaft 60 when the side handle 50 is gripped by the user.
  • two or more measurement devices are provided to each of the first and second attachment portions 42 L, 42 R in the electric work machine 1 in the aforementioned embodiments. Further, in light of this detection mechanism, the two or more measurement devices are spaced away from each other in the circumferential direction, as described in the aforementioned embodiments, thus enabling an increase in detection accuracy.
  • first and second attachment portions 42 L, 42 R may be omitted.
  • one or more attachment portions may be provided, in addition to the first and second attachment portions 42 L, 42 R.
  • the side handle 50 may be attached to a member or a part other than the gear housing 6 .
  • the side handle 50 may be attached to the motor housing 4 .
  • the side handle 50 may be fixed (or secured) to the main body 2 . That is, the side handle 50 may be undetachably attached to the main body 2 .
  • the first and second attachment portions 42 L, 42 R may be provided integrally with the main body 2 (for example, the gear housing 9 ).
  • the first and second attachment portions 42 L, 42 R may be molded integrally with the main body 2 . That is, the first and second attachment portions 42 L, 42 R may be part of the main body 2 . In other words, a portion of the main body 2 may work as the first and second attachment portions 42 L, 42 R.
  • the motor 30 may be in a form distinct from an AC motor.
  • the motor 30 may be in a form of, for example, a brushed DC motor or a brushless DC motor.
  • a DC power may be supplied to the electric work machine 1 .
  • the electric work machine 1 may be attached to a battery to drive the motor 30 with an electric power from the battery.
  • the present disclosure is not limited to a handheld electric grinder, and applicable to electric work machines in any forms, other than the handheld electric grinder.
  • the present disclosure is applicable, for example, any electric work machines, such as a driver drill, which are configured to include a handle attachable to a main body. Further, the present disclosure is applicable to electric work machines including a handle fixed to a main body in an undetachable manner.
  • Two or more functions of one element in the aforementioned embodiments may be achieved by two or more elements, and one function of one element may be achieved by two or more elements.
  • two or more functions of two or more elements may be achieved by one element, and one function achieved by two or more elements may be achieved by one element.
  • a part of the configurations in the aforementioned embodiments may be omitted.
  • at least a part of the configurations of the aforementioned embodiments may be added to or replaced with another part of the configurations of the aforementioned embodiments.
  • the present disclosure may be practiced in various modes such as a system including an electric work machine as a component, a program enabling a computer to function as the control circuit 80 , a non-transitory tangible storage medium, such as a semiconductor memory storing the above-described program, and a method of determining connecting/gripping of a handle.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Portable Power Tools In General (AREA)
  • Control Of Electric Motors In General (AREA)
  • Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)
US17/990,884 2021-12-01 2022-11-21 Technique for controlling motor in handheld electric work machine Pending US20230166379A1 (en)

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JP2021195558A JP2023081666A (ja) 2021-12-01 2021-12-01 電動作業機
JP2021-195558 2021-12-01

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20230080962A1 (en) * 2020-01-28 2023-03-16 Aesculap Ag Multi-operating-voltage motor

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WO2017051892A1 (ja) 2015-09-25 2017-03-30 株式会社マキタ グラインダ

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20230080962A1 (en) * 2020-01-28 2023-03-16 Aesculap Ag Multi-operating-voltage motor

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